The court heard that it had been going on for some time before Tainsh was snared

The engineer, of Braehead, Stirling, was today branded “absolutely disgusting” by Sheriff Derek Livingston – who said he wanted to jail him but couldn’t because his hands were tied by laws.

Falkirk Sheriff Court heard that two female admin workers at the Grangemouth-based firm had complained that items on their desks were being interfered with when they went home at night.

They told how bottles of water they had left to use again the next day were “smelling funny”.

As a result, the manager of the company rigged up a temporary, secret CCTV system in October this year.

When it was checked the next day, Tainsh – who had been working late – was seen unzipping his trousers, inserting his privates into the neck of bottles he had picked out the bin and placing them on the women’s desks after he had finished with them.

He did the same with partly-full water bottles from on top of their desks and at one point he could been seen on CCTV taking an empty chewing gum container out of a bin, performing a sex act into it and putting it on one of the women’s desks.

The court heard that this had been going on for some time before Tainsh was snared.

Prosecutor Samanatha Brown said: “The inference was that the women may well have drunk out of bottles affected.

“What drew their attention was that bottles that had been left on their desks had been moved around.”

The court heard that one of the two women had suffered sickness and stomach trouble after Tainsh was unmasked.

“That being said, I’m not sure how much good it would do and I take into account the fact that you’re a first offender and statutorily I’m not entitled to impose custody unless I’m satisfied that there’s no alternative.”

He added: “Both these women suspected there was something wrong with their bottles, but they were not unreasonable to assume that a bottle that was sitting on their desk the previous day would be OK to use.”

A court insider said: “You could hear the intake of breath from the public benches as the stomach-churning details emerged.”